Hepatozoon infections in dogs and cats in USA: History, life cycle, and suggestions for uniform terminology for hepatozoonosis in endotherms and ectotherms

Authors: Dubey, Jitender; GAD, BANETH - Hebrew University Of Jerusalem

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2025
Publication Date: 1/27/2025
Citation: Dubey, J.P., Gad, B. 2025. Hepatozoon infections in dogs and cats in USA: History, life cycle, and suggestions for uniform terminology for hepatozoonosis in endotherms and ectotherms. Veterinary Parasitology. 334. Article e110408. https://doi.org/10.1016/j.vetpar.2025.110408.
DOI: https://doi.org/10.1016/j.vetpar.2025.110408

Interpretive Summary: Hepatozoons are single celled parasites transmitted by arthropods. They can cause serious disease in companion animals and their life cycle stages are difficult to distinguish from other important related pathogens of animals. Here, the authors report criteria to distinguish Hepatozoon species in tissues of dogs. These results will be of interest to pathologists, veterinarians, and parasitologists.

Technical Abstract: Hepatozoonosis can cause serious illness in dogs in the USA resulting in muscle weakness and bone deformities. It is often fatal, and treatment is expensive and not curative. There are two recognized species of Hepatozoon which infect dogs, Hepatozoon canis and Hepatozoon americanum, transmitted by ticks, Rhipicephalus sanguineus sensu lato and Amyboloma maculatum, respectively. Hepatozoon canis has worldwide distribution and H. americanum is currently confined to the USA. Wildlife reservoirs of H. americanum have not been established but coyote (Canis latrans) is suspected, and infection is common. Most cases of hepatozoonosis in dogs in USA are thought to be due to H. americanum. However, molecular evidence suggests that a minor portion of cases in dogs are due to H. canis, sometimes as coinfection. Hepatozoonosis in domestic and wild felids, caused by Hepatozoon felis and Hepatozoon silvestris, but also H. canis, has been reported from several countries but little is known of its occurrence in domestic cats or wild felids in the USA. Here, life cycle stages of Hespatozoon spp. in dogs are compared and illustrated. Recently, a new species of Hepatozoon, Hepatozoon rufi, was described from bobcats in Mississippi, USA. There is considerable confusion concerning the terminology for different developmental stages in the life cycle of mammalian Hepatozoon spp. Here, the authors review hepatozoonosis in dogs and cats in the USA and propose a uniform terminology for the life cycle stages.